1. Field of the Invention
This invention relates to a continuous casting equipment for continuously casting molten metal supplied from a converter or the like.
2. Description of the Related Art
A continuous casting equipment is disclosed in (refer to Japanese Patent Laid-Open Application No. 63-220951 (Japanese Patent Application No. 62-51125)) and is shown in FIGS. 10a to 10e. Referring to FIGS. 10a to 10e, the continuous casting equipment shown includes a ladle exchanging apparatus 201 provided uprightly on an upper face of a side portion of a platform 217. The ladle exchanging apparatus 201 includes at least two arms 201a provided for pivotal motion independent of each other such that a ladle 203 is removably held thereon similarly as in a conventionally known ladle exchanging apparatus. A travel passageway 211 is provided in parallel to the ladle exchanging apparatus 201 on the other side portion of the upper face of the platform 217. The travel passageway 211 includes a pair of parallel rails 211a and a base 211b on which the rails 211a are supported. A travelling truck 202 has a plurality of travelling wheels 218 on a bottom face thereof and has a pair of guide wheels 219 on the opposite sides thereof. The guide wheels 219 are guided by the rails 211a such that the travelling truck 202 is moved back and forth linearly along the travel passageway 211 between a mold 208 and a skimming section 210 provided on the platform 217. The mold 208 is similar to that which is employed conventionally in a continuous casting equipment while the skimming section 210 is a recessed spacing formed to extend upwardly and downwardly through the platform 217 and includes a skimmed substance accommodating pot 215.
As shown in FIGS. 10c and 10d, a skimming window hole 214 is formed to extend through a substantially central portion of the travelling truck 202 and a cover 214a is provided for opening and closing movement on the skimming window hole 214. A turning frame 202b is provided for horizontal turning movement at a front portion of the truck 202. A tiltable frame 202a having a substantially chute-shaped section is mounted for tilting movement in upward and downward directions around a pair of supporting shafts 212 on an upper face of the turning frame 202b such that it extends from a front end of the truck 202. For such pivotal motion, a pair of tilting cylinders 220 are supported for pivotal motion on the turning frame 202b and each has a piston rod 220a connected to the tiltable frame 202a, and the tundish 204 is supported exchangeably in the tiltable frame 202a by way of a pin shaft 221.
A frame 222 is installed at a front end of the tiltable frame 202a, and a heating apparatus 202c is mounted for adjustment in position on the frame 222. For example, a known plasma heating apparatus or induction heating apparatus can be suitably employed as the heating apparatus 202c. A molten metal pouring valve opening 205 is provided at a front end side of a bottom portion of the tundish 204, and a slide valve or the like is employed as a valve for the valve opening 205 and a molten metal pouring nozzle 209 is removably provided for the valve opening 205. Meanwhile, a skimming valve opening 206 similarly employing a slide valve or the like is provided at a bottom portion of the ladle 203 and a skimming nozzle 207 is removaly fitted in the skimming valve opening 206. In this instance, the skimming valve opening 206 of the ladle 203 is set at a position just opposing to the position of an axis of turning motion of the tundish 204 (position of the center of turning motion of the turning frame 202b) when the ladle 203 is turned on the tundish 204 by way of one of the arms 201a as shown in FIGS. 10a and 10b. Consequently, the skimming location of the ladle 203 is fixed and invariable over all of the steps of a turning procedure when the tundish 204 is turned from its standby position (b) to its casting position (a) and the molten metal receiving location of the tundish 204 is fixed. Accordingly, turning movement of the tundish 204 while receiving molten metal is facilitated. Meanwhile, a skim gate 213 for discharging substances to be skimmed such as ground metal or scum is opened on a side wall face of the tundish 204 remote from the molten metal pouring valve opening 205 as shown in FIG. 10e.
The continuous casting equipment having such construction as described above is used in the following manner in continuous casting. The arms 201a of the ladle exchanging apparatus 201 are retracted away from the travel passageway 211, and the tundish 204 on the travelling truck 202 stopped at a position not shown is turned to the standby position (b) perpendicular to the travel passageway 211 as indicated by an alternate two long and short dashes line by way of the turning frame 202b. Then, maintenance or repair of the molten metal pouring valve opening 205 and/or skim gate 213 is performed, and maintenance of the heating apparatus 202c, a casting preparing operation such as heating of the tundish 204 by the heating apparatus 202c and so forth are performed. Simultaneously, the ladle 203 filled with molten metal is loaded onto one of the empty arms 201a of the ladle exchanging device 201 and is then turned by way of the arms 201a to a position above the tundish 204 for which such preparing operation has been completed. Then, the skimming nozzle 207 is set in position between the tundish 204 and the skimming valve opening 206 of the ladle 203 and is then sealed, and then the valve of the skimming valve opening 206 is opened so that molten metal in the ladle 203 is poured into the tundish 204. After a predetermined amount of molten metal is accumulated in the tundish 204, heating of the molten metal by the heating apparatus 202c is started while minimizing the opening of the valve of the skimming valve opening 206. Then, the tundish 204 is turned to its casting position (a) while receiving molten substance at a minimum flow rate from the ladle 203 and while being continuosly heated by the heating apparatus 202c. After the tuning movement of the tundish 204 to the casting position (a) is completed, the molten metal pouring nozzle 209 is set in position between the molten metal valve opening 205 of the tundish 204 and the mold 208 and is then sealed, and then the valve of the molten metal pouring valve opening 205 of the tundish 204 is opened to start continuous casting. During such continuous casting, upon continuous casting, when casting of all of the molten metal in the ladle 203 is completed, the skimming nozzle 207 thereof is moved away from the position and the empty ladle 203 is turned to its retracted position while another ladle 203, filled with molten substance and already loaded on the other arm 201a, is turned to its casting position, at which the molten metal is skimmed into the tundish 204 by way of a connection of the skimming nozzle 207. Consequently, casting can be continued successively.
Upon completion of such casting, the valve of the skimming valve opening 206 of the ladle 203 is closed and a remaining amount of molten metal in the tundish 204 is monitored, and the valve of the molten metal pouring valve opening 205 of the tundish 204 is closed after completion of such casting, thereby completing the casting operation. Subsequently, the ladle 203 is turned to move away from the position above the tundish 204, and ground metal, scum and so forth remaining in the tundish 204 are heated into a molten condition by the heating apparatus 202c. The travelling truck 202 is moved to its skimming position (c) as shown in FIG. 10e, and the molten substance to be skimmed is discharged from the skim gate 213 of the tundish 204 by tilting the tiltable frame 202a around the supporting shafts 212 and opening the skimming window hole 214 of the truck 202 so that it is accommodated into the accommodating pot 215 of the skimming section 210. After such skimming is completed, the tiltable frame 202 is returned to move the tundish 204 to its horizontal position, and then the travelling truck 202 is moved again to and stopped at the casting position (a) to perform a next casting preparing operation. Meanwhile, in order to exchange the tundish 204 itself, a clamp 216 for the tiltable frame 202a on which the tundish 204 is directly supported is released as illustrated in FIG. 10c, and the tundish 204 is carried out by means of a crane or the like to exchange the tundish 204.
With the continuous casting equipment described above, continuous casting and continuous continuous casting as well as continuous casting of different types of steel and so forth can be performed efficiently with simple and compact construction including the single ladle exchanging apparatus 210 formed from a ladle turret or the like which is conventionally employed, the single tundish travelling truck 202 and the single tundish 204 provided for turning movement and also for tilting movement on the truck 202 and having the heating apparatus 202c thereon. However, the continuous casting equipment has such problems as described below.
1 Since the horizontally turnable turning frame 202b having a turning mechanism provided thereon is carried at a front portion of the travelling truck 202 and the tiltable frame 202a having a substantially chute-shaped section and having a tilting mechanism provided thereon is provided on the upper face of the frame 202b, the travelling truck 202 has a generally great overall height. Besides, since the tundish 204 must be mounted on the tiltable frame 202b provided in such a manner as to be projected from the front end of the truck 202 such that it extends above the mold 208 and besides the tundish 204 must be turned in such condition, the travelling truck 202 is liable to fall down and besides a high load is applied to the front wheels of the truck 202. Further, while the conventional equipment is constituted such that, in order to prevent such possible falling down of the travelling truck 202, the guide wheels 219 are provided on the opposite sides of the travelling truck 202 and are guided by the rails 211a provided on the base 211b having an inverted L-shaped section, and in order to allow the travelling truck 202 to bear a high load, the front wheels have a great diameter and/or a great width, such construction naturally has a limitation, and particularly in the case wherein the tundish 204 has a great capacity for the continuous casting for a cast article of a great sectional area, the travelling truck 202 is excessively great in overall size. Further, no such travelling wheel 218 can bear such load, and also construction for the prevention of falling down of the travelling truck 202 is great in size, and besides the safety in casting operation is susceptible. Consequently, the continuous casting equipment is not in practical use.
2 On the other hand, while ground metal, scum and so forth which remain in the tundish 204 after completion of casting are discharged from the skim gate 213 of the tundish 204 and accommodated in the accommodating pot 215 of the skimming section 210 by moving the travelling truck 202 to its skimming position (c), tilting the tiltable frame 202a around the supporting shafts 212 and opening the skimming window hole 214 of the truck 202, since the tiltable frame 202a can be tilted, particularly in the case of the tundish 204 of a large capacity for the continuous casting for a cast piece of a great sectional area, by only 45 degrees at the greatest taking the safety into consideration because the piston rods 220a of the tilting cylinders 220 supported for pivotal motion on the turning frame 202b are connected to the tilting frame 202a and the tundish 204 is only secured in the tilting frame 202a by means of the pin shaft 221, ground metal, scum and so forth in the tundish 204 cannot flow out completely. Further, since the distance from the skim gate 213 to the accommodating pot 215 is great, ground metal, scum and so forth are likely scattered.